Acer aspire 4520 problem

Hello,i have an acer aspire 4520 laptop which i received on october of 2008. i have recently found out that my adaptor light is blinking when it is plugged directly into my computer and is making a funny buzzing sound. My computer would not turn on at all but when the adaptor piece is not plugged directly into the computer the light remains solid green on the adaptor. Also when the adaptor is plugged in to the computer the computer is not picking up the adaptor and is not charging